Southern California -- this just in

Critical debris basins along the San Gabriel Mountains are near capacity or overflowing as another band of rain and thunderstorms bears down on the charred foothills this afternoon, prompting officials to order more evacuations as they brace for the possibility of more damaging mudslides.

Evacuation orders are in place for about 500 homes in parts of La Cañada Flintridge, La Crescenta and Acton. At least 41 houses have been damaged or destroyed in a hillside neighborhood in La Cañada Flintridge. The city of Sierra Madre, where saturated foothills are threatening to break loose, has also issued evacuation orders.

"I hate to say this, but there might be more damage," said Nicole Nishida, spokeswoman for the Los Angeles County Sheriff's Department, noting that two large debris basins above La Cañada Flintridge are full. A Red Cross shelter has been set up at La Cañada High School. Residents whose cars were destroyed or stuck in mud have been ferried to the shelter by deputies.

The evacuations in Sierra Madre include all streets above Churchill and Canyon Crest; all streets above Brookside and Sturtevant; all streets above Lotus Lane at Camillo; and the private sections of Auburn Avenue above Elm Street.

The Los Angeles County Department of Public Works said mud and debris flows are also possible in La Cañada Flintridge, La Crescenta, Glendale, Sunland-Tujunga, Soledad Canyon, Acton and Aliso Canyon. Information is available at the Department of Public Works website.

The National Weather Service has extended its flash-flood warning for the San Gabriel Mountain foothills until 2:45 p.m. as more showers and thunderstorms move into the region.

"Any additional rainfall will result in continued mud and debris flow activity at least through the mid-afternoon hours," according to a National Weather Service statement.

The storm that moved in Friday had not been expected to sit over the Los Angeles region so long, but an overnight high pressure ridge over the central United States unexpectedly stalled and preventing the weather front from swiftly moving out. The intensity of the predawn rains appeared to catch residents and officials alike by surprise.

Authorities are most concerned this afternoon about the northern edge of Ocean View Boulevard near Manistee Drive in La Cañada Flintridge, a neighborhood that was deluged by a river of mud, rocks and trees as it bore the double blow of a collapsing hillside and an overflowing debris basin overnight.

At least five homes have been tagged as uninhabitable and at least six other are inundated with mud and debris. About 25 vehicles were damaged when they were struck by the K-rails that were put in place to protect homes. The sound and smell of hissing gas wafted through the neighborhood in the late morning and workers were out capping gas lines.

Crews were taking advantage of a respite from the heavy rains and were feverishly working to clear out the clogged and overflowing Mullally Debris Basin, at the northern tip of Ocean View Boulevard, and the Pickens Canyon debris basis near Ocean View and Foothill boulevards. Bulldozers were shoveling out muddy water, boulders and debris in anticipation of more rain.

Debris basins are designed to hold in mud, rocks and trees to prevent them from smashing into homes.

L.A. County Fire Capt. Richard Baligad said that he estimates one boulder inside the Mullally basin weighs between six to ten tons. That caused the flooding, he said.

"It came from who knows where up there," he said, pointing up at the muddy hillside. "Once that thing got plugged, they [residents] were done." A forklift was digging away at the boulder, and in early going was able only to scratch it.

A public works official on the scene said workers hoped to be able to clear away enough debris to free a clogged 60-inch drain pipe.

The hillside above the homes at Ocean View and Manistee came down just as the basin began to overflow, inundating them in a rumbling instant.

"We are just going to keep monitoring the situation and be ready for emergencies," said Capt. Drew Smith of the Los Angeles County Fire Department.

The homes that were most severely damaged are at the base of hills charred by the Station Fire, where blackened trees are now washed away.

Elsewhere, the flooding led to the closing of portions of several Southern California freeways Saturday. The Long Beach Freeway was closed in both directions at Willow Avenue in Long Beach at about 4:30 a.m. because of flooding, CHP Officer Francisco Villalobos said. Caltrans was called, and some lanes were opened at 8:33 a.m. and the entire freeway was back to normal about a half hour later.

All lanes of the northbound Interstate 5 at Lankershim Boulevard in Sun Valley were closed from 7 a.m. to 9 a.m. until Caltrans could clear the way, Villalobos said.

Just after the I-5 was opened, flooding caused authorities to close the transition of the southbound 110 to the northbound U.S. 101 near downtown Los Angeles for about a half-hour.

Topanga Canyon Boulevard was closed at about 4 a.m. between Pacific Coast Highway and Grand View, south of Malibu, Villalobos said. The CHP did not know when it would open. Villalobos said there had been reports of a rock slide but no confirmation.

In addition, the Balboa Boulevard offramp off the eastbound 118 in Granada Hills was closed at 7:25 a.m. because of flooding. It remained closed.

Brian Humphrey, a spokesman for the Los Angeles Fire Department, said the calls his department has received have been minor, including reports of mud on the curbs and trees down. There have been no mandatory evacuation orders within the city's 470 square miles, but the department was closely monitoring hillsides. Scattered power outages have affected thousands of customers served by Southern California Edison and the Department of Water and Power.